Electric induction apparatus



April 10,- 1951 I. H. SCLATER ELECTRIC INDUCTION APPARATUS Filed Feb. 5, 19

Invent or: Ivan hoe H. Sclaoer,

His Attornqg.

Patented Apr. 10, 1951 ELECTRIC INDUCTION APPARATUS Ivanhoe H. Sclater, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application February 5, 1946, Serial No. 645,650

Claims.

This invention relates to electric induction apparatus and more particularly to improvements in cores for such apparatus and to the method of making such cores.

With the advent of modern core material, such as cold rolled silicon strip steel, which is characterized by having very much lower losses when the flux is in the lengthwise direction or direction of rolling than when the flux is at right angles to this direction, the major problem in the construction of cores has been the problem of making the best utilization of the properties of this material. This is especially important because this material is more costly than the old material, such as so-called hot rolled steel in which there is very little grain effect, that is, diiference in magnetic properties for flux travel in different directions. As a result a large number of different core constructions have been produced. In general these are characterized by (1) either reversing the ordinary direction of the laminations so that the laminae are superposed on each other radially or, in other words, are nested one layer within the other, and the laminae are bent or wound around the core corners so that the flux travels with the grain or most favorable magnetic direction throughout the core, or (2) the laminae are fiat stacked in the conventional manner but their ends are cut on the bias or mitered so that there is minimum cross grain flux travel at the 'mitered core joints. As the wound or bent type cores must be strain relief annealed in order to keep down the losses, such cores have heretofore been limited in size because of the very large annealing furnace or oven which would be required to anneal a completed wound or bent core suitable for use with large power transformers. Furthermore, in order to link such a core with a winding or windings of the apparatus it is usually necessary to have substantial additional free space surrounding the apparatus whereby the core can either be threaded through the winding window and rewound in place or else the core can be cut in one or more turn lengths and threaded through the winding Window and all of these operations require a substantial amount of floor space.

This invention is characterized by making the leg portions of the core in the conventional oldstyle fiat-stacked manner and by making the yoke portions of the core by the bent or wound technique. Stated another way, the core may be said to consist of conventional fiat-stacked straightleg portions with end sheets which are fiatwise 2 bent or curved instead of being flat and interleaved in the conventional manner.

The yoke portions of the core may ordinarily be U-shaped portions which together may constitute two complementary halves of a separately-formed relatively-small wound or bent iron core. The leg and yoke portions of the core may be separately annealed, in which case the parts may be placed very close together in an oven or they may be annealed one at a time, but in either case the dimensions of the annealing furnace or oven can be very much smaller than the over-all dimension of the completed core.

An object of the invention is to provide a new and improved electric induction apparatus.

Another object of the invention is to provide a new and improved magnetic core for electric induction apparatus.

A further object of the invention is to provide a novel method of making a magnetic core for electric induction apparatus.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a perspective view of an electric induction apparatus embodying the invention, Fig. 2 illustrates one step in a method of making the yoke portions of my core, Figs. 3 and 4 illustrate successive steps in the method and Fig. 5 illustrates how the various parts are fitted together to form my novel core, Fig. 6 illustrates a modified form of yoke construction,

and Fig. '7 illustrates in section an electric in-' duction apparatus provided with a modified form of core having yoke portions made from the parts shown in Fig. 6.

Referring now to the drawing and more particularly to Fig. 1, there is shown therein a conductive winding l which is linked by a divided or two-part magnetic core 2. The two parts of the core are ordinarily duplicates and, as will be seen in Fig. 1, they each consist of two generally U- shaped yoke portions 3 and 4 and two straight leg portions 5. The innermost or central leg portions 5 form the winding leg of the core and of course are invisible, being inside the window of the coil I. The two core parts maybe held together by respective clamping bands 6.

The yoke portions 3 and 4 may be made in any suitable manner. For example, as shown in Fig. 2, a plurality of strips of grain oriented magnetic material may be cut to form a package 1 in which the pieces have progressively increasing length from bottom to top. A similarly cut package of 3 longer pieces 8 may be placed on top of the package 1 and, likewise, additional packages 9 and I may be placed on top thereof. All of the pieces may have a central hole or perforation which is preferably a plurality of laminae in each package, 7

the pieces all being aligned by holes i6 therein.

The various pieces in the variouspackages may be fitted together in any suitable way; for example, the longest pieces in the packages it) and [2 may be bent generally in the shape of a semicircle and fitted with abutting ends into a ringshaped form or press and then successively inner pairs of pieces will. be fitted in place until the ring is built up from the outside in, as shown in Fig. 3'; Pressure may be then applied so a to compact the parts and draw the joints up tight. The ring may then be pressure worked by means of either compression from the outside or expansion from the inside (by means of a contracting or expandingmandrel) into the rectangular shape shown in Fig. 4- and finally rivets or other suitable fastening means ll and i3 may be passed throughv the aligned openings i i and it so as to hold .the parts constituting the U-shaped members 3 and l tightly together. The relatively small rectangular or square-shaped core member shown in Fig. 4 may then be strain relief annealed as a 1 unit after. which its parts 3 and Q may be separated by removingthe retaining bands and pull ing them apart.

The leg portions 501" my core may be formed inthe usual or. conventional manner by cutting a plurality of flat straight strips or sheets of magnetic material of the same length and then stacking these pieces one ontopof the other. However,-the ends are staggered or overlapped by an amount corresponding to the stagger or overlap of the butt joints between the ends of the packages inthe yoke part 3 and 5-. Thus, legs suitable-for use with the U shaped yoke parts 3 and 4: wi-lli-consist ofiio'ur packages it, 20, and 22,

the ends of the packages being stepped or stag t gered tocorrespond with the staggered ends of the packages forming the yoke members. The leg members 5 being perfectly straight can easily be annealed and will occupy minimum space in a furnace'or ovenas they will be all solid magnetic material.

Fig. 5 shows how the leg portions 5 are fitted together with the U-shaped yoke portions and 4 to-form a closed rectangular core having staggered overlapping butt joints and having continuous unbroken magnetic material at all of the corners so that the flux stays in each lamination piecethroughout the complete magnetic circuit and ha minimum tendency to migrate across the core in a radial direction because of the fact that the laminae-are'separated or nested radially.

It'will be'relatively easy to link a core such as shown in Fig. 5 with a conductive winding or windings as either or both of the U-shaped yoke members 3 and t when not in place make it easy to slip-a winding into the core window around either one or both of the straight winding legs.

Another way of making the yoke portions of the core is shown in Fig. 6. In this figure a relatively long strip of grain-oriented magnetic-material is wound on a mandrel into the form shown. This wound core, which is indicated at 23, is then strain relief annealed and finally out completely through in two places by straight cuts 24 and 25. The cuts are not directly opposite each other so that the two U-shaped portions 55 and i which are formed have unequal length legs.

These parts are combined with straight flat stacked leg portions 5 to form the modified core shown in Fig. '7. The legs 5 differ from the legs 5 of Figs. 1 and 5 in that the ends of the packages of laminae are zigzagged instead of progressing in a stepped manner. The length of the zigzag, that is to say, the amount of lengthwise displacement of adjacent packages in the legs 5, is equal to the difierence in length of the legs of the U- shaped portions 3 and i in Fig. 6 which are formed by the cuts 24 and 25.

After a conductive winding i has been fitted over a pair of legs 5 and the outer legs 5 have been put in position the core i end sheeted, so to speak; by separating the two U-shaped parts of the wound cut core of Fig. 6 into packets which are alternately reversed and whose ends are fitted against the staggered ends of the leg portions 5. In other words, one package 26 taken from the inside of the upper half 3 crime cut wound core 23' and of a thickness corresponding to the thickness of the leg packages forms an unsymmetrical U-shaped package 26 which is fitted into place so as to join the ends of the legs 5 and 5'. The next yoke package 2'! is taken from the part 3' of the cut wound core 23 but is reversed end for end so that the long end is the left-hand end and the right-hand end is the shcrt end and this package is then fitted into abutting relation with the corresponding packagesof the leg members 5. In this manner the yoke portions are built up and are joined to the leg members with overlapping butt joints which are clearly shown in completed form in the left-hand part of Fig. '7.

While there have been shown and described particular embodiments of thisinvention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by able magnetic direction parallel to their length to form two straight laminated leg portions with the ends of their laminae staggered, arranging said-leg portions on opposite sides of a core Window with the planes of their laminae perpendicular to the face of saidwindcw, and end sheeting said core by connecting the. corresponding ends of corresponding laminae in the two legs with fiatwise bent additional strips of the same magnetic material.

2. A long legged rectangular magnetic core comprising, in combination, two separately-preformed long straight legs, and two pre-formed generally U-shaped. bundles of radially nested fiatwise curved magnetic laminations, theends of said U-shaped bundles of laniinations having complementary unevenly spaced surfaces which will interfit to make low reluctance magnetic joints, said bundles being separated by a distance corresponding to the length of said long legs, said long'legs each comprising a bundle of straight flat laminations of magnetic material, said legs being spaced apart parallel to each other with the longitudinal center lines of all their laminations in the same plane which constitutes the plane of the window of said long legged core, the planes of the individual leg laminations being perpendicular to the plane of said Window, one pair of adjacent ends of the respective long legs having uneven surfaces which are complementary respectively to the ends of one of said U- shaped bundles and being interconnected by said U-shaped bundles with said complementary ends interfitted to form low reluctance joints, the other pair of adjacent ends of the respective long legs having uneven surfaces which are complementary respectively to the ends of the other of said U-shaped bundles and being interconnected by said other U-shaped bundle with said complementary ends interfitted to form low reluctance joints, the curved center lines of all of the laminations in both of said U-shaped bundles being in the same plane with the straight longitudinal center lines of said leg laminations.

3. The method of making a long legged rectangular magnetic core which includes flatwise bending and cutting magnetic strip material to form two short legged generally U-shaped bundles of radially nested laminations, fiat stacking a plurality of long straight flat laminations of magnetic material to form two spaced parallel long leg members, interconnecting two adjacent ends of said long leg members with one of said U-shaped bundles of laminations, and interconmeeting the other two adjacent ends of said long leg members with the other of said U-shaped bundles.

4. The method of making a long legged rectangular magnetic core which includes cutting and fiatwise bending magnetic strip material to form two short legged generally U-shaped b-undles of radially nested laminations, flat stacking a plurality of long straight flat laminations of magnetic material to form two spaced parallel long leg members, interconnecting two adjacent ends of said long leg members with one of said bundles of laminations and interconnecting the other two adjacent ends of said long leg members with the othe of said U-shaped bundles.

5. The method of making a long legged rectangular magnetic core including the steps of forming a short legged magnetic core of radially nested flatwise curved laminations, providing joints in the legs or said short legged core, separating said short legged core at said joints, joining one end of one leg of each part of said short legged core with a straight long laminated core leg, and joining the remaining ends of the short legs of said short legged core with another straight longlaminated leg for said long legged core.

IVANI-IOE H. SCLATER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,102,513 Johannesen July '7, 1914 1,365,569 Troy Jan. 11, 1921 1,935,426 Acly Nov. 14, 1933 2,058,362 Smalley Oct. 20, 1936 2,344,294 Evans Nov. 14, 1944 2,380,300 Gaston July 10, 1945 2,408,211 Hodnette Sept. 24, 1946 2,411,374 Horstman Nov. 19, 1946 FOREIGN PATENTS Number Country Date 106,986 Great Britain June 14. 1917 

